Liquid crystal q-plates: classical and quantum photonic applications

Liquid crystals (LC) are particularly well suited for the manipulation of the angular momentum of light. Only recently, the possibility of coupling the LCs and the so-called orbital angular momentum (OAM) of light has been identified. OAM is associated with a light beam having a helical wavefront and an optical vortex at its axis. A singular-patterned LC plate, named “q-plate”, can be used for generating and controlling helical beams of light, or “vortex beams”. The q- plate can be also used in the quantum regime, for controlling the OAM of single photons, leading to several applications in the quantum information field.